Lubricating-oil composition

ABSTRACT

The lubricating oil composition of the present invention comprises a base oil that contains at least one selected from the group consisting of a mineral oil and a synthetic oil, has a viscosity index of 120 or more, and has a paraffin content by ring analysis of 70% or more; (A) a dispersant containing one or more compounds selected from the group consisting of an alkenylsuccinimide, a boronated alkenylsuccinimide, an alkylsuccinimide and a boronated alkylsuccinimide; and (B) a metallic detergent containing one or more compounds selected from the group consisting of an alkali metal sulfonate, an alkali metal phenate, an alkali metal salicylate, an alkaline earth metal sulfonate, an alkaline earth metal phenate, and an alkaline earth metal salicylate; wherein the component (A) is contained in an amount of from 0.01% by mass to 0.10% by mass in terms of the nitrogen content thereof based on the total amount of the composition, the component (B) is contained in an amount of from 0.01% by mass to 0.3% by mass in terms of the metal content thereof based on the total amount of the composition, at least one or more compounds selected from the group consisting of a boronated alkenylsuccinimide and a boronated alkylsuccinimide in the component (A) are contained, the ratio by mass of boron to nitrogen B/N in the component (A) is 0.5 or more, the phosphorus content based on the total amount of the composition is from 100 ppm by mass to 1200 ppm by mass, and the sulfated ash content based on the total amount of the composition is 1.1% by mass or less. Accordingly, even when used in automobile internal combustion engines capable of increasing the thermal and mechanical durability temperature thereof more than before and capable of realizing power increase and fuel efficiency, the lubricating oil composition can prevent engine performance degradation and therefore can satisfy both the requirements of engine performance and engine durability.

TECHNICAL FIELD

The present invention relates to a lubricating oil composition for usein internal combustion engines such as diesel engines, gasoline engines,gas engines, and hybrid vehicle engines.

BACKGROUND ART

In recent years, environmental regulations are becoming more and moresevere on a global scale, and the circumstances surrounding automobiles,including fuel efficiency requirements and exhaust emission regulations,are becoming increasingly severe. Behind this, there are environmentalissues, such as global warming, and resource protection arising fromconcerns about the depletion of petroleum resources. For these reasons,further reduction of fuel consumption in automobiles is desired.

Attempting power increase in automobile engines would tend to increasethe combustion temperature and the pressure in engines. In particular,diesel engines are required to have high-temperature resistance andrigidity and thermal cracking resistance and the like, and thereforemust be designed to be tough. However, for fuel consumption, reductionof engine weight is desired.

Given the situation, heretofore, an aluminum alloy such as JIS AC8A hasbeen used for diesel engine pistons for weight reduction. In addition, alubricating oil composition suitable for lubrication of diesel enginesusing an aluminum alloy is developed (for example, see Patent Document1).

CITATION LIST Patent Document

-   Patent Document 1: JP-A 2010-10070

SUMMARY OF INVENTION Technical Problem

However, with respect to pistons formed of an aluminum alloy, thetemperature at which they could still secure thermal and mechanicaldurability is about 350° C., and the thermal expansivity thereof at thattemperature is high, and therefore, in the recent trend to improveautomobile engines so as to meet the requirements of power increase andfuel efficiency, cast iron pistons having a thermal and mechanicaldurability temperature of up to about 400° C. have become partlyemployed in place of aluminum alloy pistons.

As compared with aluminum alloy pistons, cast iron pistons could securehigher durability and, in addition, graphite contained in cast iron hasself-lubricity, and therefore cast iron pistons could have good seizureresistance. However, there is a concern that the cast iron pistonsreadily cause engine performance degradation, since they may have a hightemperature in the vicinity of the top dead center to cause significantabrasion and poor detergency as compared with that of aluminum alloypistons.

Accordingly, an object of the present invention is to provide alubricating oil composition which, even when used in automobile internalcombustion engines capable of increasing the thermal and mechanicaldurability temperature thereof more than before and capable of realizingpower increase and fuel efficiency, can prevent engine performancedegradation and therefore can satisfy both the requirements of engineperformance and engine durability.

Solution to Problem

The inventors of the present invention conducted intensive studies and,as a result, found that the problem can be overcome by a lubricating oilcomposition containing a base oil, a dispersant and a metallic detergentin which these components are blended under a specific condition, andaccomplished the present invention.

Specifically, the lubricating oil composition of the present inventioncomprises a base oil that contains at least one selected from the groupconsisting of a mineral oil and a synthetic oil, has a viscosity indexof 120 or more, and has a paraffin content by ring analysis of 70% ormore; a dispersant (A) containing one or more compounds selected fromthe group consisting of an alkenylsuccinimide, a boronatedalkenylsuccinimide, an alkylsuccinimide and a boronatedalkylsuccinimide; and a metallic detergent (B) containing one or morecompounds selected from the group consisting of an alkali metalsulfonate, an alkali metal phenate, an alkali metal salicylate, analkaline earth metal sulfonate, an alkaline earth metal phenate, and analkaline earth metal salicylate; wherein the component (A) is containedin an amount of from 0.01% by mass to 0.10% by mass in terms of thenitrogen content thereof based on the total amount of the composition,the component (B) is contained in an amount of from 0.01% by mass to0.3% by mass in terms of the metal content thereof based on the totalamount of the composition, one or more compounds selected from the groupconsisting of a boronated alkenylsuccinimide and a boronatedalkylsuccinimide in the component (A) are contained, the ratio by massof boron to nitrogen B/N in the component (A) is 0.5 or more, thephosphorus content based on the total amount of the composition is from100 ppm by mass to 1200 ppm by mass, and the sulfated ash content basedon the total amount of the composition is 1.1% by mass or less.

A production method for the lubricating oil composition of the presentinvention is a production method for a lubricating oil composition forproducing a lubricating oil composition by blending, with a base oilthat contains at least one selected from the group consisting of amineral oil and a synthetic oil, has a viscosity index of 120 or more,and has a paraffin content by ring analysis of 70% or more, a dispersant(A) containing one or more compounds selected from the group consistingof an alkenylsuccinimide, a boronated alkenylsuccinimide, analkylsuccinimide and a boronated alkylsuccinimide, and a metallicdetergent (B) containing one or more compounds selected from the groupconsisting of an alkali metal sulfonate, an alkali metal phenate, analkali metal salicylate, an alkaline earth metal sulfonate, an alkalineearth metal phenate, and an alkaline earth metal salicylate, so that thecomponent (A) is contained in an amount of from 0.01% by mass to 0.10%by mass in terms of the nitrogen content thereof based on the totalamount of the composition, the component (B) is contained in an amountof from 0.01% by mass to 0.3% by mass in terms of the metal contentthereof based on the total amount of the composition, one or morecompounds selected from the group consisting of a boronatedalkenylsuccinimide and a boronated alkylsuccinimide in the component (A)are contained, the ratio by mass of boron to nitrogen B/N in thecomponent (A) is 0.5 or more, the phosphorus content based on the totalamount of the composition is from 100 ppm by mass to 1200 ppm by mass,and the sulfated ash content based on the total amount of thecomposition is 1.1% by mass or less.

Advantageous Effects of Invention

According to the present invention, it is possible to provide alubricating oil composition which, even when used in automobile internalcombustion engines capable of increasing the thermal and mechanicaldurability temperature thereof more than heretofore and then capable ofrealizing power increase and fuel efficiency, can prevent engineperformance degradation and therefore can satisfy both the requirementsof engine performance and engine durability.

DESCRIPTION OF EMBODIMENTS [Lubricating Oil Composition]

The lubricating oil composition of the present invention comprises abase oil that contains at least one selected from the group consistingof a mineral oil and a synthetic oil, has a viscosity index of 120 ormore, and has a paraffin content by ring analysis of 70% or more; adispersant (A) containing one or more compounds selected from the groupconsisting of an alkenylsuccinimide, a boronated alkenylsuccinimide, analkylsuccinimide and a boronated alkylsuccinimide; and a metallicdetergent (B) containing one or more compounds selected from the groupconsisting of an alkali metal sulfonate, an alkali metal phenate, analkali metal salicylate, an alkaline earth metal sulfonate, an alkalineearth metal phenate, and an alkaline earth metal salicylate.

The component (A) is contained in an amount of from 0.01% by mass to0.10% by mass in terms of the nitrogen content thereof based on thetotal amount of the composition, the component (B) is contained in anamount of from 0.01% by mass to 0.3% by mass in terms of the metalcontent thereof based on the total amount of the composition.

One or more compounds selected from the group consisting of a boronatedalkenylsuccinimide and a boronated alkylsuccinimide in the component (A)are contained, and the ratio by mass of boron to nitrogen B/N in thecomponent (A) is 0.5 or more. In addition, in the lubricating oilcomposition, the phosphorus content based on the total amount of thecomposition is from 100 ppm by mass to 1200 ppm by mass, and thesulfated ash content based on the total amount of the composition is 1.1% by mass or less. The lubricating oil composition of the presentinvention may be hereinafter referred to simply as “the presentcomposition”.

[Base Oil]

The base oil in the present composition may be mineral oil or syntheticoil. The type of the mineral oil and the synthetic oil is notspecifically limited, and for use herein, any one may be suitablyselected from a mineral oil and a synthetic oil heretofore used as thebase oil in lubricating oil compositions.

Examples of the mineral oil include a mineral oil refined by subjectinga lubricating oil distillate that is obtained by distilling under areduced pressure the atmospheric residue given by atmosphericdistillation of crude oil, to one or more treatments selected fromsolvent deasphalting, solvent extraction, hydro-cracking, solventdewaxing, catalytic dewaxing, hydrorefining and the like, and a mineraloil produced by isomerization of wax or GTL WAX and the like.

Examples of the synthetic oil include polybutene, polyolefins [α-olefinhomopolymers and copolymers (e.g., ethylene-α-olefin copolymers)],various kinds of esters (for example, polyol esters, dibasic acidesters, phosphate esters), various kinds of ethers (for example,polyphenyl ethers), polyglycols, alkylbenzenes, alkylnaphthalenes, etc.Among those synthetic oils, polyolefins and polyol esters areparticularly preferred from the viewpoint of the viscositycharacteristics thereof, the solubility of additives therein, and thecompatibility thereof to seal rubber.

In the present invention, the above mineral oils may be used alone or incombination of two or more thereof. Alternatively, the above syntheticoils may be used alone or in combination of two or more thereof.Furthermore, one or more of the mineral oils and one or more of thesynthetic oils may be used in combination thereof.

Not specifically limited, the viscosity of the base oil may be selectedin accordance with the use of the lubricating oil composition. Regardingthe viscosity of the base oil, the kinematic viscosity thereof at 100°C. is generally from 2 mm²/s to 30 mm²/s, preferably from 3 mm²/s to 15mm²/s, more preferably from 4 mm²/s to 10 mm²/s. When the kinematicviscosity at 100° C. is 2 mm²/s or more, the evaporation loss is small,and when the kinematic viscosity at 100° C. is 30 mm²/s or less, thepower loss owing to viscosity resistance could be prevented thereforerealizing an effect of fuel efficiency improvement.

The paraffin content by ring analysis (hereinafter this may be referredto as % C_(P)) of the base oil is 70% or more. When % C_(P) is less than70%, then the oxidation stability of the composition is poor and theacid value thereof may increase and sludge may form in the composition.From the above-mentioned viewpoints, % C_(P) is preferably 80% or more.

Further, the viscosity index of the base oil is 120 or more, and ispreferably 125 or more, more preferably 130 or more. The base oil ofwhich the viscosity index is less than 120 undergoes great viscositychange owing to temperature change therefore reducing the effect of fuelefficiency improvement at low temperatures.

[Component (A)]

The component (A) is a dispersant that contains one or more compoundsselected from the group consisting of an alkenylsuccinimide, a boronatedalkenylsuccinimide, an alkylsuccinimide and a boronatedalkylsuccinimide.

Among one or more compounds selected from the group consisting of analkenylsuccinimide, a boronated alkenylsuccinimide, an alkylsuccinimideand a boronated alkylsuccinimide for the component (A), either theboronated alkenylsuccinimides or the boronated alkylsuccinimides isessential. When the component (A) contains the boronatedalkenylsuccinimide or the boronated alkylsuccinimide, thehigh-temperature detergency of the composition can be improved.

In this embodiment, the succinimide includes a monoimide structure and abisimide structure.

The monoimide structure includes both a structure based on an alkenyl oralkylsuccinic monoimide alone and a structure based on a boronatedalkenyl or alkylsuccinic monoimide. The alkenyl or alkylsuccinicmonoimide includes, for example, an alkenyl or alkylsuccinic monoimiderepresented by the following formula (1).

Similarly, the bisimide structure includes both a structure based on analkenyl or alkylsuccinic bisimide alone and a structure based on aboronated alkenyl or alkylsuccinic bisimide. The alkenyl oralkylsuccinic bisimide includes, for example, an alkenyl oralkylsuccinic bisimide represented by the following formula (2).

In the above formulae (1) and (2) , R¹, R³ and R⁴ each represent analkenyl group or an alkyl group, and the mass-average molecular weightof the group is preferably from 500 to 3,000, more preferably from 1,000to 3,000, respectively.

When the mass-average molecular weight of R¹, R³ and R⁴ is 500 or more,the solubility in the base oil is high and when 3,000 or less, thedetergent effect can be expected. R³ and R⁴ may be the same ordifferent.

R², R⁵ and R⁶ each represent an alkylene group having from 2 to 5 carbonatoms, and R⁵ and R⁶ may be the same or different. m indicates aninteger of from 1 to 10, and n indicates 0 or an integer of from 1 to10. Here, m is preferably from 2 to 5, more preferably from 3 to 4. Whenm is 2 or more, the composition can realize further betterhigh-temperature detergency, and when m is 5 or less, the solubility inthe base oil can be further better.

In the above formula (2), n is preferably from 1 to 4, more preferablyfrom 2 to 3. Different from that in the case of monoimide, when n is 1or more, the high-temperature detergency of the composition is furtherbetter, and when n is 4 or less, the solubility in the base oil can befurther better.

The alkenyl group includes, for example, a polybutenyl group, apolyisobutenyl group, and an ethylene-propylene copolymer. The alkylgroup includes ones derived from hydrogenation of those groups. As apreferred alkenyl group, there is mentioned a polybutenyl group or apolyisobutenyl group. The polybutenyl group is favorably obtained as oneproduced from a mixture of 1-butene and isobutene or throughpolymerization of high-purity isobutene. Specific examples of apreferred alkyl group include those prepared though hydrogenation of apolybutenyl group or a polyisobutenyl group.

The above alkenyl or alkylsuccinimide may be produced generally throughreaction of an alkenylsuccinic anhydride, which is obtained throughreaction of a polyolefin and a maleic anhydride or an alkylsuccinicanhydride which is obtained through hydrogenation of the alkenylsuccinicanhydride, with a polyamine. The above succinic monoimide and succinicbisimide maybe produced by varying the reaction ratio of thealkenylsuccinic anhydride or the alkylsuccinic anhydride and thepolyamine.

As the olefin monomer to form the above polyolefin, usable is/are onealone or two or more of α-olefins having from 2 to 8 carbon atoms,either singly or as combined. Preferred is use of a mixture of isobuteneand 1-butene.

On the other hand, the polyamine includes a simple diamine such asethylenediamine, propylenediamine, butylenediamine, andpentylenediamine; a polyalkylenepolyamine such as diethylenetriamine,triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine,di(methylethylene)triamine, dibutylenetriamine, tributylenetetramine,and pentapenthylenehexamine; a piperazine derivative such asaminoethylpiperazine.

The boronated alkenyl or alkyl succinimide may be one produced accordingto a conventional method.

For example, the above polyolefin is reacted with a maleic anhydride toprepare an alkenylsuccinic anhydride, and then further reacted forimidization with an intermediate that is obtained through reaction ofthe above polyamine and a boron compound such as boron oxide, boronhalide, boric acid, boric anhydride, borate, ammonium borate.

With respect to the component (A), the ratio by mass of the monoimidestructure-derived nitrogen to the bisimide structure-derived nitrogen(Nm/Nb) is 0.5 or less, preferably 0.4 or less. The ratio by mass(Nm/Nb) of 0.5 or less could improve engine durability.

One or more compounds selected from the group consisting of analkenylsuccinimide, a boronated alkenylsuccinimide, an alkylsuccinimideand a boronated alkylsuccinimide in the component (A) are contained inan amount of from 0.01% by mass to 0.10% by mass in terms of thenitrogen content thereof based on the total amount of the composition.More preferably, the content is from 0.02% by mass to 0.09% by mass, andeven more preferably from 0.03% by mass to 0.08% by mass. When thecontent of the compounds is less than 0.01% by mass in terms of thenitrogen content thereof, the high-temperature detergency of thecomposition would be poor, but when more than 0.10% by mass, theoxidation stability would worsen.

The ratio by mass of boron to nitrogen (B/N ratio) in the boronatedalkenyl or alkylsuccinimide in the component (A) is 0.5 or more,preferably 0.6 or more, more preferably 0.8 or more. The B/N ratio of0.5 or more could greatly improve the high-temperature detergency of thecomposition.

Presence of at least a predetermined amount of the boron content derivedfrom the boronated alkenyl or alkylsuccinimide in the component (A)makes the composition exhibit high-temperature detergency. When theboron content derived from the boronated alkenyl or alkylsuccinimide inthe component (A) is from 0.01% by mass to 0.06% by mass based on thetotal amount of the composition, the composition can realizes sufficienthigh-temperature detergency. Preferably, the boron content is from 0.02%by mass to 0.05% by mass.

[Component (B)]

The component (B) in the lubricant oil composition of the presentinvention is a metallic detergent that contains one or more compoundsselected from the group consisting of an alkali metal sulfonate, analkali metal phenate, an alkali metal salicylate, an alkaline earthmetal sulfonate, an alkaline earth metal phenate, and an alkaline earthmetal salicylate. Among them, as the component (B), preferred is atleast either alkali metal sulfonates or alkaline earth metal sulfonates.

The alkaline earth metal sulfonate includes an alkaline earth metal saltof an alkylaromatic sulfonic acid which is obtained through sulfonationof an alkylaromatic compound having a molecular weight of from 300 to1,500, preferably from 400 to 700. In particular, there are mentionedmagnesium salts, calcium salts and the like, and above all, preferred isuse of calcium salts.

The alkaline earth metal phenate includes an alkaline earth metal saltof an alkylphenol, an alkylphenol sulfide, or a Mannich reaction productof an alkylphenol, especially a magnesium salt, a calcium salt or thelike thereof; and above all, preferred is use of the calcium salts.

The alkaline earth metal salicylate includes an alkaline earth metalsalts, especially a magnesium salt, a calcium salt or the like of analkylsalicylic acid; and above all, preferred is use of the calciumsalts.

The alkyl group constituting the alkaline earth metal detergent ispreferably one having from 4 to 30 carbon atoms, and is more preferablyan alkyl group having from 6 to 18 carbon atoms. The alkyl group may beeither linear or branched. The group may be a primary alkyl group, asecondary alkyl group or a tertiary alkyl group.

The alkaline earth metal sulfonates, the alkaline earth metal phenatesand the alkaline earth metal salicylates include neutral alkaline earthmetal sulfonates, neutral alkaline earth metal phenates and neutralalkaline earth metal salicylates that are obtained through directionreaction of the above alkylaromatic sulfonic acid, alkylphenol,alkylphenol sulfide, a Mannich reaction product of an alkylphenol,alkylsalicylic acid or the like with an alkaline earth metal base suchas an oxide and a hydroxide of one or more alkaline earth metalsselected from magnesium and calcium.

In addition, the alkaline earth metal sulfonates, the alkaline earthmetal phenates and the alkaline earth metal salicylates also includeneutral alkaline earth metal sulfonates, neutral alkaline earth metalphenates and neutral alkaline earth metal salicylates that are obtainedthrough conversion of the above alkylaromatic sulfonic acid,alkylphenol, alkylphenol sulfide, a Mannich reaction product of analkylphenol, alkylsalicylic acid or the like into alkaline metal saltssuch a sodium salts and potassium salts thereof followed by substitutionthereof with an alkaline earth metal salt to give the intended salts.

Further, the alkaline earth metal sulfonates, the alkaline earth metalphenates and the alkaline earth metal salicylates include basic alkalineearth metal sulfonates, basic alkaline earth metal phenates and basicalkaline earth metal salicylates that are obtained by heating theneutral alkaline earth metal sulfonates, neutral alkaline earth metalphenates and neutral alkaline earth metal salicylates along with anexcessive alkaline earth metal salt or alkaline earth metal base in thepresence of water.

Still further, the alkaline earth metal sulfonates, the alkaline earthmetal phenates and the alkaline earth metal salicylates includeoverbased alkaline earth metal sulfonates, overbased alkaline earthmetal phenates and overbased alkaline earth metal salicylates that areobtained through reaction of the neutral alkaline earth metalsulfonates, neutral alkaline earth metal phenates and neutral alkalineearth metal salicylates with carbonate or borate of an alkaline earthmetal in the presence of carbon dioxide.

One alone or two or more selected from the above alkaline earth metalsulfonates, alkaline earth metal phenates and the alkaline earth metalsalicylates may be used here either alone or as combined.

As the metallic detergent, the above neutral salt, basic salt, overbasedsalt or a mixture thereof may be used, and in particular, a mixture ofone or more of an overbased salicylate, an overbased phenate and anoverbased sulfonate, and a neutral sulfonate is preferred, from theviewpoints of detergency for engine inside parts and in abrasionresistance. The metallic detergent is commercially sold generally in theform of being diluted with a light lubricant base oil or the like and isavailable as such. Preferably, the metal content of the metallicdetergent for use herein is from 1.0% by mass to 20% by mass, morepreferably from 2.0% by mass to 16% by mass.

The base number of the component (B) is preferably from 10 mg KOH/g to600 mg KOH/g, more preferably from 20 mg KOH/g to 500 mg KOH/g. Thetotal base number as referred to herein means the total base numberaccording to potentiometric titration (base number—perchloric acidmethod) to be measured according to 7. “Petroleum Products andLubricants—Neutralization Number Test Method” in JIS K 2501.

The metal ratio in the component (B) is not specifically limited. Ingeneral, one or more metallic detergents having a metal ratio of 20 orless may be used. It is especially desirable that a metallic detergenthaving a metal ratio of 3 or less, more preferably 1.5 or less, evenmore preferably 1.2 or less is used as the essential component from theviewpoint of being more excellent in oxidation stability, base numberretention and high-temperature detergency and the like. The metal ratioas referred to herein is represented by (number of valences of metalelement in metallic detergent)×(metal element content (mol %))/(soapgroup content (mol %)). The metal element means calcium, magnesium,etc.; and the soap group means a sulfonic acid group, a phenol group, asalicylic acid group, etc.

In the lubricating oil composition of the present invention, the amountof the component (B) is preferably 0.3% by mass or less in order thatthe sulfated ash content therein could be reduced to 1.1% by mass orless. The blending amount of the component (B) is from 0.01% by mass to0.3% by mass in terms of the metal content thereof based on the totalamount of the composition.

More preferably, the component (B) contains sodium sulfonate in anamount of 0.05% by mass or less as the metal amount thereof based on thetotal amount of the lubricating oil composition, for the purpose ofreducing the sulfated ash content in the lubricating oil composition to1.1% by mass or less. Alternatively, magnesium sulfonate is contained inan amount of 0.05% by mass or less as the metal amount thereof based onthe total amount of the lubricating oil composition.

In the lubricating oil composition of the present invention, the sulfurcontent is preferably 0.3% by mass or less based on the total amount ofthe composition, more preferably 0.2% by mass or less, even morepreferably 0.1% by mass or less based on the total amount of thecomposition. The sulfur content of 0.3% by mass or less is preferred ascapable of effectively preventing the exhaust gas purification catalystperformance from degrading.

[Component (C)]

Preferably, a zinc dialkyldithiophosphate (hereinafter this may bereferred to as “ZnDTP”) is further blended with the present compositionas a component (C). The component (C) includes, for example, ZnDTPrepresented by the following formula (3).

In the above formula (3), R¹¹, R¹², R¹³ and R¹⁴ each represent asubstituent selected from a primary or secondary alkyl group having from3 to 22 carbon atoms or an alkylaryl group substituted with an alkylgroup having from 3 to 18 carbon atoms, and they may be the same ordifferent each other.

In the present invention, one alone or two or more types of those ZnDTPsmay be used either singly or as combined. Especially preferred is onethat comprises, as the main ingredient, a zinc dithiophosphate withsecondary alkyl groups for enhancing abrasion resistance.

Specific examples of ZnDTP include zinc dipropyldithiophosphate, zincdibutyldithiophosphate, zinc dipentyldithiophosphate, zincdihexyldithiophosphate, zinc diisopentyldithiophosphate, zincdiethylhexyldithiophosphate, zinc dioctyldithiophosphate, zincdinonyldithiophosphate, zinc didecyldithiophosphate, zincdidodecyldithiophosphate, zinc dipropylphenyldithiophosphate, zincdipentylphenyldithiophosphate, zinc dipropylmethylphenyldithiophophate,zinc dinonylphenyldithiophosphate, zinc didodecylphenyldithiophosphate,zinc didodecylphenyldithiophosphate, etc.

[Other Components]

If desired, an antioxidant, a viscosity index improver, a pour-pointdepressant, a rust inhibitor, a metal deactivator, a defoaming agent, ananti-wear agent, an extreme-pressure agent and any other additives maybe added to the lubricating oil composition of the present inventionwithin a range not to impair the effects of the present invention.

<Antioxidant>

As the antioxidant, antioxidants such as phenol-based or amine-based maybe used.

The phenol-based antioxidant includes, for example, octadecyl3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate;4,4′-methylenebis(2,6-di-t-butylphenol); 4,4′-bis(2,6-di-t-butylphenol);4,4′-bis(2-methyl-6-t-butylphenol):2,2′-methylenebis(4-ethyl-6-t-butylphenol);2,2′-methylenebis(4-methyl-6-t-butylphenol);4,4′-butylidenebis(3-methyl-6-t-butylphenol);4,4′-isopropylidenebis(2,6-di-t-butylphenol);2,2′-methylenebis(4-methyl-6-nonylphenol);2,2′-isobutylidenebis(4,6-dimethylphenol);2,2′-methylenebis(4-methyl-6-cyclohexylphenol);2,6-di-t-butyl-4-methylphenol; 2,6-di-t-butyl-4-ethylphenol;2,4-dimethyl-6-t-butylphenol; 2,6-di-t-amyl-p-cresol;2,6-di-t-butyl-4-(N,N′-dimethylaminomethylphenol);4,4′-thiobis(2-methyl-6-t-butylphenol);4,4′-thiobis(3-methyl-6-t-butylphenol);2,2′-thiobis(4-methyl-6-t-butylphenol);bis(3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide;bis(3,5-di-t-butyl-4-hydroxybenzyl) sulfide; n-octyl3-(4-hydroxy-3,5-di-t-butylphenyl)propionate; n-octadecyl3-(4-hydroxy-3,5-di-t-butylphenyl)propionate;2,2′-thio[diethyl-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate],etc. Among them, especially preferred are bisphenol compounds and estergroup-containing phenol compounds.

The amine-based antioxidant includes, for example,monoalkyldiphenylamines such as monooctyldiphenylamine andmonononyldiphenylamine; dialkyldiphenylamines such as4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine,4,4′-dihexyldiphenylamine, 4,4′-diheptyldiphenylamine,4,4′-dioctyldiphenylamine and 4,4′-dinonyldiphenylamine;polyalkyldiphenylamines such as tetrabutyldiphenylamine,tetrahexyldiphenylamine, tetraoctyldiphenylamine andtetranonyldiphenylamine; as well as naphtylamine-based antioxidants, inparticular, α-naphtylamine, phenyl-α-naphthylamine, and furtheralkyl-substituted phenyl-α-naphthylamines such asbutylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine,hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine,octylphenyl-α-naphthylamine and nonylphenyl-α-naphthylamine. Among them,diphenylamine compounds are preferred to naphtylamine compounds from theviewpoint of the antioxidation effect thereof.

In the present invention, a molybdenumamine-based antioxidant may befurther added. The molybdenumamine-based antioxidant usable hereincludes those prepared by the reaction of a hexavalent molybdenumcompound, specifically molybdenum trioxide and/or molybdic acid, with anamine compound, for example, the compounds obtained according to theproduction method described in JP-A 2003-252887.

The amine compound to be reacted with a hexavalent molybdenum compoundis not specifically limited. In particular, there are mentionedmonoamines, diamine, polyamines and alkanolamines. More particularly,there are exemplified alkylamines having an alkyl group with from 1 to30 carbon atoms (in which the alkyl group may be linear or branched)such as methylamine, ethylamine, dimethylamine, diethylamine,methylethylamine and methylpropylamine; alkenylamines having an alkenylgroup with from 2 to 30 carbon atoms (in which the alkenyl group may belinear or branched) such as ethenylamine, propenylamine, butenylamine,octenylamine and oleylamine; alkanolamines having an alkanol group withfrom 1 to 30 carbon atoms (in which the alkanol group may be linear orbranched) such as methanolamine, ethanolamine, methanolethanolamine andmethanolpropanolamine; alkylenediamines having an alkylene group withfrom 1 to 30 carbon atoms such as methylenediamine, ethylenediamine,propylenediamine and butylenediamine; polyamines such asdiethylenetriamine, triethylenetetramine, tetraethylenepentamine andpentaethylenehexamine; compounds derived from the above monoamines,diamines or polyamines by incorporating thereinto an alkyl group oralkenyl group having from 8 to 20 carbon atoms, such asundecyldiethylamine, undecyldiethanolamine, dodecyldipropanolamine,oleyldiethanolamine, oleylpropylenediamine andstearyltetraethylenepentamine; heterocyclic compounds such as imidazole;alkylene oxide adducts of those compounds; mixture of those compounds,etc. Also exemplified here are sulfur-containing molybdenum complexeswith succinimide and the like described in JP-B 3-22438 and JP-A2004-2866.

The blending amount of the above antioxidant is preferably from 0.3% bymass to 3% by mass based on the total amount of the composition, fromthe viewpoint of the miscibility thereof with the base oil. Morepreferably, the amount of the above antioxidant is from 0.4% by mass to3% by mass, even more preferably from 0.4% by mass to 2% by mass, stillmore preferably from 0.5% by mass to 2% by mass. When the content of theantioxidant is 0.3% by mass or more based on the total amount of thecomposition, then the acid value of the composition can be preventedfrom increasing, and when 3% by mass or less, the solubility in thelubricant base oil can be secured.

<Viscosity Index Improver>

The viscosity index improver includes, for example, polymethacrylates,dispersant-type polymethacrylates, olefinic copolymers (for example,ethylene-propylene copolymers), dispersant-type olefinic copolymers,styrenic copolymers (for example, styrene-diene copolymers,styrene-isoprene copolymers), etc. The blending amount of the viscosityindex improver may be from 0.5% by mass to 15% by mass, preferably from1% by mass to 10% by mass based on the total amount of the composition,from the viewpoint of the blending effect.

<Pour-Point Depressant>

The pour-point depressant includes ethylene-vinyl acetate copolymers,condensates of chlorinated paraffin and naphthalene, condensates ofchlorinated paraffin and phenol, polymethacrylates, polyalkylstyrenes,etc. For example, preferred for use herein are polymethacrylates havinga mass-average molecular weight of from 5,000 to 50,000. The pour-pointdepressant may be used in a ratio of from 0.1% by mass to 5% by massbased on the total amount of the composition.

<Rust Inhibitor>

The rust inhibitor includes petroleum sulfonates, alkylbenzenesulfonates, dinonylnaphthalene sulfonates, alkenylsuccinates,polyalcohol esters, etc. The blending amount of the rust inhibitor maybe from 0.01% by mass to 1% by mass, preferably from 0.05% by mass to0.5% by mass based on the total amount of the composition, from theviewpoint of the blending effect.

<Metal Deactivator>

The metal deactivator (copper corrosion inhibitor) includes, forexample, benzotriazole compounds, tolyltriazole compounds, thiadiazolecompounds, imidazole compounds, pyrimidine compounds, etc. Among them,preferred are benzotriazole compounds. Incorporating the metaldeactivator can protect engine parts from metal corrosion and oxidativedegradation. The blending amount of the metal deactivator is preferablyfrom 0.01% by mass to 0.1% by mass, more preferably from 0.03% by massto 0.05% by mass based on the total amount of the composition, from theviewpoint of the blending effect.

<Defoaming Agent>

The defoaming agent includes silicone oil, fluorosilicone oil,fluoroalkyl ether, etc. From the viewpoint of the balance of thedefoaming effect and the economic performance, the agent is blendedpreferably in an amount of from 0.005% by mass to 0.1% by mass based onthe total amount of the composition.

<Anti-Wear Agent or Extreme-Pressure Agent>

The anti-wear agent or the extreme-pressure agent includessulfur-containing compounds such as zinc dithiophosphate, zincphosphate, zinc dithiocarbamate, molybdenum dithiocarbamate, molybdenumdithiophosphate, disulfides, olefin sulfides, sulfurized oils and fats,sulfurized esters, thiocarbonates, thiocarbamates and polysulfides;phosphorus-containing compounds such as phosphites, phosphates,phosphonates, and amine salts or metal salt of those compounds; sulfurand phosphorus-containing anti-wear agents such as thiophosphites,thiophosphates, thiophosphonates, and amine salts or metal salts ofthose compounds.

In case where the additional anti-wear agent or extreme-pressure agentis incorporated, if desired, the amount of the additional anti-wearagent or extreme-pressure agent to be blended may be 600 ppm by mass orless in terms of the element of zinc and based on the total amount ofthe lubricating oil composition. Preferably, the amount is from 0 ppm bymass to 500 ppm by mass, more preferably from 0 ppm by mass to 400 ppmby mass.

Also the amount of the additional anti-wear agent or extreme-pressureagent to be blended is 500 ppm by mass or less in terms of the elementof phosphorus and based on the total amount of the lubricating oilcomposition. Preferably, the amount is from 0 ppm by mass to 400 ppm bymass, more preferably from 0 ppm by mass to 300 ppm by mass. When thezinc amount is 600 ppm by mass or less and the phosphorus amount is 500ppm by mass or less, a problem of extremely shortening the period foroil change owing to consumption of the basic compound in the lubricatingoil composition, for example, in the engine oil could be evaded.

<Phosphorus Content and Sulfated Ash Content in Lubricating OilComposition>

In the lubricating oil composition of the present invention, thephosphorus content based on the total amount of the composition is from100 ppm by mass to 1200 ppm by mass. When the phosphorus amount is lessthan 100 ppm by mass, the wear resistance would be insufficient. On theother hand, when the phosphorus content is more than 1200 ppm by mass,purification catalyst poisoning by exhaust gas could not be sufficientlyprevented.

The phosphorus content is preferably from 200 ppm by mass to 1100 ppm bymass, more preferably from 300 ppm by mass to 1000 ppm by mass, evenmore preferably from 400 ppm by mass to 900 ppm by mass.

In the lubricant oil composition of the present invention, the sulfatedash content is 1.1% by mass or less based on the total amount of thecomposition. When the sulfated ash content is more than 1.1% by mass,the amount of ash to deposit on the DPF filter in a diesel engine wouldincrease whereby the DPF filter would be readily clogged by ash and thelife of the DPF filter would be thereby shortened.

From the viewpoint of further increasing the oxidation stability, thebase number retention and the high-temperature detergency of thelubricating oil composition, the sulfated ash content is more preferably0.2% by mass or more, even more preferably 0.3% by mass or more. Fallingwithin the range, the composition can maintain the base number and thehigh-temperature detergency for a longer period of time.

The sulfated ash content means the ash content which is determined byfiring a sample of the composition, then adding sulfuric acid to theresultant carbonized residue and heating it to have a constant weight.In general, the sulfated ash content is used for identifying a roughamount of a metal additive in a lubricant oil composition. Specifically,it is determined according to the method prescribed in JIS K 2272 “5.Sulfated Ash Content Test Method”.

The lubricating oil composition of the present invention is not onlyexcellent in high-temperature detergency but also has good compatibilitywith fluoro-rubber seal much used inside engines, and therefore can befavorably used in internal combustion engines such as gasoline engines,diesel engines, gas engines and hybrid vehicle engines. As internalcombustion engines, there are mentioned ordinary internal combustionengines that are produced using various materials such as aluminum alloymaterials, nickel chromium alloy materials, carbon steel materials andchromium molybdenum steel materials. The lubricating oil composition ofthe present invention is especially favorable for use for lubricatinginternal combustion engines in which at least the piston head is formedof a cast iron material.

[Production Method for Lubricating Oil Composition]

The production method for a lubricating oil composition of thisembodiment of the present invention is a production method for alubricating oil composition, which comprises blending, with a base oilthat contains at least one selected from the group consisting of amineral oil and a synthetic oil, has a viscosity index of 120 or more,and has a paraffin content by ring analysis of 70% or more, a dispersant(A) containing one or more compounds selected from the group consistingof an alkenylsuccinimide, a boronated alkenylsuccinimide, analkylsuccinimide and a boronated alkylsuccinimide, and a metallicdetergent (B) containing one or more compounds selected from the groupconsisting of an alkali metal sulfonate, an alkali metal phenate, analkali metal salicylate, an alkaline earth metal sulfonate, an alkalineearth metal phenate, and an alkaline earth metal salicylate, so that thecomponent (A) is contained in an amount of from 0.01% by mass to 0.10%by mass in terms of the nitrogen content thereof based on the totalamount of the composition, the component (B) is contained in an amountof from 0.01% by mass to 0.3% by mass in terms of the metal contentthereof based on the total amount of the composition, at least one ormore compounds selected from the group consisting of a boronatedalkenylsuccinimide and a boronated alkylsuccinimide in the component (A)are contained, the ratio by mass of boron to nitrogen B/N in thecomponent (A) is 0.5 or more, the phosphorus content based on the totalamount of the composition is from 100 ppm by mass to 1200 ppm by mass,and the sulfated ash content based on the total amount of thecomposition is 1.1% by mass or less.

The production method for a lubricating oil composition of thisembodiment of the present invention may further comprise blending, ifdesired, with the above base oil, any of an antioxidant, a viscosityindex improver, a pour point depressant, a rust inhibitor, a metaldeactivator, a defoaming agent, an anti-wear agent, an extreme-pressureagent and any other additive.

In addition, as described above, the lubricating oil compositionproduced by blending, with the base oil, the component (A) and thecomponent (B) and, if desired, any of an antioxidant, a viscosity indeximprover, a pour point depressant, a rust inhibitor, a metaldeactivator, a defoaming agent, an anti-wear agent, an extreme-pressureagent and any other additive contains those various additives blendedthereinto. In the lubricating oil composition, at least a part of thosevarious additives blended therein may react with each other to form anyother compound therein in some cases.

EXAMPLES

The present invention is described in more detail with reference toExamples hereinunder. The present invention is not limited to thefollowing Examples.

Examples and Comparative Examples

Using a base oil, a dispersant, a metallic detergent and any otheradditive mentioned below, samples of a lubricating oil composition wereproduced, and tested for the characteristics and the properties thereofaccording to the evaluation methods mentioned below. The results areshown in Table 1 and Table 2.

Base oil: hydrorefined oil, kinematic viscosity at 40° C.; 21 mm²/s,kinematic viscosity at 100° C.; 4.5 mm²/s, viscosity index; 127, %C_(P); 83, % C_(A); 0.0, sulfur content; less than 10 ppm by mass, NOACKvalue; 13.3% by mass.

Viscosity index improver A: polymethacrylate, weight-average molecularweight 420,000, resin amount 39% by mass.

Phenol-based antioxidant: octadecyl3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate

Amine-based antioxidant: dialkyldiphenylamines, nitrogen content 4.62%by mass.

Zinc dithiophosphate: Zn content 9.0% by mass, phosphorus content 8.2%by mass, sulfur content 17.1% by mass, alkyl group; mixture of secondarybutyl group and secondary hexyl group.

Metallic detergent A: neutral calcium sulfonate, base number (perchloricacid method) 20 mg KOH/g, calcium content 1.8% by mass, sulfur content1.8% by mass.

Metallic detergent B: neutral calcium sulfonate, base number (perchloricacid method) 22 mg KOH/g, calcium content 2.4% by mass, sulfur content3.0% by mass.

Metallic detergent C: overbased calcium sulfonate, base number(perchloric acid method) 308 mg KOH/g, calcium content 12% by mass,sulfur content 1.1% by mass.

Metallic detergent D: overbased calcium sulfonate, base number(perchloric acid method) 320 mg KOH/g, calcium content 13% by mass,sulfur content 2.4% by mass.

Metallic detergent E: overbased calcium sulfonate, base number(perchloric acid method) 450 mg KOH/g, calcium content 15% by mass,sulfur content 1.2% by mass.

Metallic detergent F: overbased calcium sulfonate, base number(perchloric acid method) 500 mg KOH/g, calcium content 18.5% by mass.

Metallic detergent G: overbased calcium phenate, base number (perchloricacid method) 200 mg KOH/g, calcium content 7.2% by mass, sulfur content2.0% by mass.

Metallic detergent H: overbased calcium phenate, base number (perchloricacid method) 255 mg KOH/g, calcium content 9.2% by mass, sulfur content3.3% by mass.

Metallic detergent I: overbased calcium phenate, base number (perchloricacid method) 400 mg KOH/g, calcium content 14% by mass, sulfur content2% by mass.

Metallic detergent J: neutral calcium salicylate, base number(perchloric acid method) 64 mg KOH/g, calcium content 2.3% by mass.

Metallic detergent K: overbased sodium sulfonate, base number(perchloric acid method) 450 mg KOH/g, sodium content 19.5% by mass,sulfur content 1.2% by mass.

Metallic detergent L: overbased magnesium sulfonate, base number(perchloric acid method) 410 mg KOH/g, magnesium content 9.4% by mass,sulfur content 2.0% by mass.

Metallic detergent M: overbased calcium salicylate, base number(perchloric acid method) 230 mg KOH/g, calcium content 7.9% by mass.

Metallic detergent N: overbased calcium salicylate, base number(perchloric acid method) 290 mg KOH/g, calcium content 7.8% by mass.

Ashless dispersant A: boron derivative of alkenylsuccinimide,number-average molecular weight of polybutenyl group 1000, nitrogencontent 1.8% by mass, boron content 2.0% by mass.

Ashless dispersant B: alkenylsuccinimide, number-average molecularweight of polybutenyl group 2000, nitrogen content 1.0% by mass.

Methylbenzotriazole derivative: 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole

Other additives: pour-point depressant and defoaming agent

[Characteristics Evaluation of Base Oil and Lubricating Oil Composition](1) Kinematic Viscosity of Base Oil and Lubricating Oil Composition

Measured according to “Petroleum Product Kinematic Viscosity TestMethod” prescribed in JIS K 2283.

(2) Viscosity Index of Base Oil

Measured according to “Petroleum Product Kinematic Viscosity TestMethod” prescribed in JIS K 2283.

(3) Sulfur Content in Base Oil

Measured according to JIS K 2541.

(4) % C_(A) of Base Oil

The proportion (percentage) of the aromatic component is calculatedthrough n-d-M ring analysis.

(5) % C_(P) of Base Oil

The proportion (percentage) of the paraffin component is calculatedthrough n-d-M ring analysis.

(6) NOACK Value of Base Oil

Measured according to JPI-5S-41-2004.

(7) Boron Content

Measured according to JPI-5S-38-92.

(8) Nitrogen Content

Measured according to JIS K 2609.

(9) Molybdenum and Phosphorus Content

Measured according to JPI-5S-38-92.

(10) Sulfated Ash Content

Measured according to JIS K 2272.

[Evaluation Method] <High-Temperature Detergency Evaluation Method (HotTube Test)>

The high-temperature detergency was evaluated in a hot tube testaccording to JPI-5S-55-99. Specifically, a sample oil and an air wereintroduced into a glass tube having an inner diameter of 2 mm, at flowrates of 0.31 mL/h and 10 mL/min, respectively, for 16 hours. The glasstube was kept at 280° C. Subsequently, the mass of the deposit adheringto the glass tube was measured. The samples were evaluated in 10 ranks.The higher rank means that the mass of the deposit was small and thesample is excellent in high-temperature detergency.

<Initial Coating Film Formation Test>

Using a Soda four-ball machine and under the condition of an oiltemperature of 80° C., a rotation number of 500 rpm and a load of 0.0480MPa, the time in which the rotating ball and the fixed ball wereelectrically completely insulated by the lubricating oil film wasevaluated as the film formation time within a test period of 180seconds. The samples having taken a shorter film formation time are moreexcellent in the initial coating film formability and in the anti-wearperformance.

<Load Carrying Performance Test>

Using a Soda four-ball machine and under the condition of an oiltemperature of 80° C. and a rotation number of 500 rpm, a loadincreasing from the initial load of 0.048 MPa up to 0.288 MPa atintervals of 0.196 MPa every 3 minutes was kept applied to the sample,and the load under which the rotating ball and the fixed ballelectrically completely run through the sample was evaluated as thecomplete contact load. The samples for which the complete contact loadwas larger are more excellent in load carrying performance.

TABLE 1 Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Base Oil Amass % balance balance balance balance balance balance balance balancebalance balance balance balance balance balance balance balance balanceViscosity Index Improver A mass % 5.00 5.00 5.00 5.00 5.00 5.00 5.005.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 Phenol-basedAntioxidant mass % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.500.50 0.50 0.50 0.50 0.50 0.50 0.50 Amine-based Antioxidant mass % 0.500.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.500.50 0.50 Zinc Dithiophosphate mass % 0.30 0.30 0.30 0.30 0.30 0.30 0.300.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Metallic Detergent Amass % 5.00 5.00 Metallic Detergent B mass % 3.85 Metallic Detergent Cmass % 0.78 Metallic Detergent D mass % 0.72 Metallic Detergent E mass %0.59 Metallic Detergent F mass % 0.49 0.26 0.26 Metallic Detergent Gmass % 1.25 Metallic Detergent H mass % 0.98 Metallic Detergent I mass %0.63 Metallic Detergent J mass % 3.89 Metallic Detergent K mass % 0.560.26 Metallic Detergent L mass % 0.90 0.44 Metallic Detergent M mass %1.13 Metallic Detergent N mass % 1.15 Ashless Dispersant A mass % 1.002.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.002.00 2.00 Ashless Dispersant B mass % 2.00 2.00 2.00 2.00 2.00 2.00 2.002.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Methylbenzotriazolemass % 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.050.05 0.05 0.05 0.05 Derivative Other Additive mass % 0.50 0.50 0.50 0.500.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 Calciummass % 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.00 0.000.09 0.09 0.05 0.05 Magnesium mass % 0.00 0.00 0.00 0.00 0.00 0.00 0.000.00 0.00 0.00 0.00 0.00 0.08 0.00 0.00 0.00 0.04 Sodium mass % 0.000.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.11 0.00 0.00 0.000.05 0.00 Phosphorus mass % 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.020.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Zinc mass % 0.03 0.03 0.03 0.030.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Boronmass % 0.02 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.040.04 0.04 0.04 0.04 Nitrogen mass % 0.06 0.08 0.08 0.08 0.08 0.08 0.080.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 Nitrogen (derived fromashless mass % 0.04 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.060.06 0.06 0.06 0.06 0.06 0.06 dispersant) Sulfated Ash Content mass %0.37 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.37 0.37 0.380.38 0.38 0.38 High-Temperature M.R. 8.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.09.0 9.0 9.0 9.0 9.0 9.0 8.0 8.0 Detergency Test (hot tube test score)Initial Coating Film sec 14 5 5 4 5 6 8 7 5 4 27 30 52 6 8 33 20Formation Test (coating film formation time) Load Carrying MPa 0.288<0.288< 0.288< 0.288< 0.288< 0.288< 0.288< 0.288< 0.288< 0.288< 0.288<0.288< 0.288< 0.288< 0.288< 0.288< 0.288< Performance Test (completecontact load)

TABLE 2 Comparative Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Base Oil A mass % balance balance balance balance balance balancebalance balance balance balance balance balance balance balance balancebalance balance Viscosity Index Improver A mass % 5.00 5.00 5.00 5.005.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00Phenol-based Antioxidant mass % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.500.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 Amine-based Antioxidantmass % 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.500.50 0.50 0.50 0.50 Zinc Dithiophosphate mass % 0.30 0.30 0.30 0.30 0.300.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Metallic Detergent Amass % 5.00 5.00 Metallic Detergent B mass % 3.85 Metallic Detergent Cmass % 0.78 Metallic Detergent D mass % 0.72 Metallic Detergent E mass %0.59 Metallic Detergent F mass % 0.49 Metallic Detergent G mass % 1.25Metallic Detergent H mass % 0.98 Metallic Detergent I mass % 0.63Metallic Detergent J mass % 3.89 Metallic Detergent K mass % 0.56Metallic Detergent L mass % 0.90 Metallic Detergent M mass % 1.13Metallic Detergent N mass % 1.15 Ashless Dispersant A mass % 1.00 1.001.00 Ashless Dispersant B mass % 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.002.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Methylbenzotriazole mass %0.05 0.05 0.05 0.05 0.05 0.0 50.05 0.05 0.05 0.05 0.05 0.05 0.05 0.050.05 0.05 0.05 Derivative Other Additive mass % 0.50 0.50 0.50 0.50 0.500.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 Calcium mass% 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.00 0.00 0.90 0.090.00 0.09 0.00 Magnesium mass % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000.00 0.00 0.00 0.08 0.00 0.00 0.00 0.00 0.00 Sodium mass % 0.00 0.000.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.11 0.00 0.00 0.00 0.00 0.000.00 Phosphorus mass % 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.020.02 0.02 0.02 0.02 0.02 0.00 0.00 Zinc mass % 0.03 0.03 0.03 0.03 0.030.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.00 0.00 Boron mass %0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000.02 0.02 0.02 Nitrogen mass % 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.040.04 0.04 0.04 0.04 0.04 0.04 0.06 0.06 0.06 Nitrogen (derived from mass% 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.020.04 0.04 0.04 ashless dispersant) Sulfated Ash Content mass % 0.35 0.350.35 0.35 0.35 0.36 0.36 0.35 0.35 0.35 0.35 0.34 0.35 0.35 0.31 0.010.00 High-Temperature M.R. 0 0 0 0 0 0 0 0 0 0   0   0   0 0 2   5   0  Detergency Test (hot tube test score) Initial Coating Film FormationTest (coating sec 156 152 25 121 51 58 58 72 41 180<    180<    180<   42 59 180<    180<    180<    film formation time) Load Carrying MPa0.192 0.288< 0.288< 0.288< 0.288< 0.288< 0.288< 0.288< 0.288<  0.288< 0.144  0.144 0.144 0.192  0.144  0.096  0.048 Performance Test(complete contact load)

[Evaluation Results]

From the results in Table 1, it is known that, in Examples using thelubricating oil composition of the present invention, the deposit in thehot tube test is small, and this means that the lubricating oilcomposition of the present invention is excellent in hot-temperaturedetergency. In addition, the lubricating oil composition in Examplesgave a good result in the initial coating film formation test, fromwhich it is known that, in using the lubricating oil composition of thepresent invention, oil film shortage occurs little even at the top deadcenter of pistons, or that is, the lubricating oil composition has goodanti-wear performance. Furthermore, the load-carrying performance isalso excellent.

1. A lubricating oil composition comprising: a base oil that contains atleast one selected from the group consisting of a mineral oil and asynthetic oil, has a viscosity index of 120 or more, and has a paraffincontent by ring analysis of 70% or more; (A) a dispersant containing oneor more compounds selected from the group consisting of analkenylsuccinimide, a boronated alkenylsuccinimide, an alkylsuccinimideand a boronated alkylsuccinimide; and (B) a metallic detergentcontaining one or more compounds selected from the group consisting ofan alkali metal sulfonate, an alkali metal phenate, an alkali metalsalicylate, an alkaline earth metal sulfonate, an alkaline earth metalphenate, and an alkaline earth metal salicylate; wherein the component(A) is contained in an amount of from 0.01% by mass to 0.10% by mass interms of the nitrogen content thereof based on the total amount of thecomposition, the component (B) is contained in an amount of from 0.01%by mass to 0.3% by mass in terms of the metal content thereof based onthe total amount of the composition, at least one or more compoundsselected from the group consisting of a boronated alkenylsuccinimide anda boronated alkylsuccinimides in the component (A) are contained, theratio by mass of boron to nitrogen B/N in the component (A) is 0.5 ormore, the phosphorus content based on the total amount of thecomposition is from 100 ppm by mass to 1200 ppm by mass, and thesulfated ash content based on the total amount of the composition is1.1% by mass or less.
 2. The lubricating oil composition according toclaim 1, wherein: the component (B) is at least either alkyl metalsulfonates or alkaline earth metal sulfonates, and the base number ofthe component (B) is from 10 mg KOH/g to 600 mg KOH/g.
 3. Thelubricating oil composition according to claim 1, comprising anantioxidant selected from the group consisting of an amine-basedantioxidant, a phenol-based antioxidant and a molybdenumamine-basedantioxidant, in an amount of from 0.3% by mass to 3% by mass based onthe total amount of the lubricating oil composition.
 4. The lubricatingoil composition according to claim 1, wherein the phosphorus content isfrom 200 ppm by mass to 1100 ppm by mass.
 5. The lubricating oilcomposition according to claim 1, wherein the B/N ratio is 0.6 or more.6. The lubricating oil composition according to claim 1, wherein, as thecomponent (B), sodium sulfonate is contained in an amount of 0.05% bymass or less in terms of the metal amount thereof based on the totalamount of the lubricating oil composition.
 7. The lubricating oilcomposition according to claim 1, wherein, as the component (B),magnesium sulfonate is contained in an amount of 0.05% by mass or lessin terms of the metal amount thereof based on the total amount of thelubricating oil composition.
 8. The lubricating oil compositionaccording to claim 1, which is used for lubrication in internalcombustion engines.
 9. The lubricating oil composition according toclaim 8, which is used for lubrication in internal combustion engineswhere at least a piston head thereof is formed of a cast iron material.